+lingual environment, encode filenames in UTF-8.
+
+=head1 RETURN VALUES
+
+BIO_s_file() returns the file BIO method.
+
+BIO_new_file() and BIO_new_fp() return a file BIO or NULL if an error
+occurred.
+
+BIO_set_fp() and BIO_get_fp() return 1 for success or 0 for failure
+(although the current implementation never return 0).
+
+BIO_seek() returns the same value as the underlying fseek() function:
+0 for success or -1 for failure.
+
+BIO_tell() returns the current file position.
+
+BIO_read_filename(), BIO_write_filename(), BIO_append_filename() and
+BIO_rw_filename() return 1 for success or 0 for failure.